The invention relates in general to electrophotographic and photoelectrophoretic imaging systems. More specifically, the invention concerns 3-bromo-N-2"-pyridyl-8,13-dioxodinaphtho-(2,1-b; 2',3'-d)-furan-6-carboxamide as a new composition of matter and its use in photoelectrophoretic imaging.
In general the phrase photoelectrophoretic imaging, as used herein, refers to those systems wherein electrically photosensitive particles dispersed in an insulating carrier liquid are exposed to imagewise light and an electrical field resulting in particle migration in image configuration. One such process which is capable of producing one color image, or images, in more than one color including full natural color in one step is described in detail and claimed in U.S. Pat. Nos. 3,383,993 to Yeh; 3,384,488 and 3,384,565 to Tulagin and Carreira and 3,384,566 to Clark, all issued May 21, 1968, the entire disclosures of which are incorporated herein by reference. In such an imaging system, electrically photosensitive particles are dispersed in a relatively non-conductive liquid carrier. The suspension is placed between electrodes, subjected to a potential difference and exposed to an image. As these steps are completed, selective particle migration takes place in image configuration. Where the electrical field is applied between electrodes which are in contact with the imaging suspension, normally images made up of particles are formed on one or both electrodes. In a monochromatic system, particles of only one color need be used, but particles of additional colors may be used if desired to provide a range of monochrome colors which may be reproduced. In a polychromatic system, images of more than one color may be formed by utilizing particles of more than one color which have spectral response curves which do not have substantial overlap thereby providing for color separation. In a preferred embodiment for subtractive full color imaging, yellow particles responsive to blue light, cyan particles responsive to red light and magenta particles responsive to green light are used in the suspension. Thus, when the suspension is exposed to red light, for example, the red light causes the cyan particle to move away from the surface on which the image is formed leaving behind the yellow and magenta particles which combined appear red. Further, where white light impinges the suspension, all particles migrate leaving a clear area which when the image is transferred to white paper appears white. Also, where no light impinges the suspension, all particles remain which form a dark brown or black area.
The critical component of such an imaging system is the electrically photosensitive particles. The particles must have intense and pure colors to form highly saturated images. For monochrome imaging, it is desirable that the particles be highly photosensitive so that light and power requirements are small. The requirements for polychromatic imaging are, however, much more severe in that the particles of each color cyan, yellow and magenta, for example, must have intense and pure colors and must have spectral response curves which are well-defined and do not overlap the spectral response curves for particles of other colors. Further, the photoresponse of a given particle must be to approximately the same intensity of exposure as the other particles to provide color balanced images. For example, in a subtractive system, if a particle is too photoresponsive or has too broad a spectral response, the final image will be deficient in that color. Conversely, where the particle is too "slow", the image will have a high background of that color and will have poor color balance. For additive systems, the results would be reversed.